Question

我想在mysql中的concat（）中格式化数据。但是当我尝试这样做时，mysql禁止我。这是功能：

SELECT user_id as id, DATE(leave_from) as date_from, DATE(leave_to) as date_to, NULL as delayed_checkin_remarks, NULL as early_checkout_remarks,  
        CONCAT(
        (' LeaveType : ',
        SELECT title FROM leave_type
        WHERE id = l.leave_type_id),':<br/>',leave_description) 
        as leave_remarks, leave_status
    FROM users_leave_request l 
    WHERE DATE(leave_from) between '2015-01-26' AND '2015-01-30'

问题是当我把那个＆＃39; LeaveType：＆＃39;在SELECT内部进行CONCAT之前..否则它工作正常。我该如何纠正？

Answer 1

CONCAT(

中的查询中有错位的括号

这样更好：

SELECT user_id as id, DATE(leave_from) as date_from, DATE(leave_to) as date_to, NULL as delayed_checkin_remarks, NULL as early_checkout_remarks,  
        CONCAT(
        ' LeaveType : ',
        (SELECT title FROM leave_type
        WHERE id = l.leave_type_id),':<br/>',leave_description) 
        as leave_remarks, leave_status
    FROM users_leave_request l 
    WHERE DATE(leave_from) between '2015-01-26' AND '2015-01-30'

但是，不是使用嵌套查询来获取leave_type描述，而是在主查询中的leave_type表上执行JOIN：

SELECT l.user_id as id, DATE(l.leave_from) as date_from, DATE(l.leave_to) as l.date_to, NULL as delayed_checkin_remarks, NULL as early_checkout_remarks,  
        CONCAT(' LeaveType : ', lt.title,':<br/>',l.leave_description) AS leave_remarks, 
        l.leave_status
FROM users_leave_request l              
INNER JOIN leave_type lt ON lt.id=l.l.leave_type_id         
WHERE DATE(l.leave_from) between '2015-01-26' AND '2015-01-30'

Answer 2

您还必须在Select语句周围使用引号。像这样的东西 -

SELECT user_id as id, DATE(leave_from) as date_from, DATE(leave_to) as date_to, NULL as delayed_checkin_remarks, NULL as early_checkout_remarks,  
    CONCAT(
    (' LeaveType : ',
    'SELECT title FROM leave_type
    WHERE id = l.leave_type_id)',':<br/>',leave_description) 
    as leave_remarks, leave_status
FROM users_leave_request l 
WHERE DATE(leave_from) between '2015-01-26' AND '2015-01-30'

在concat函数mysql中格式化

2 个答案: